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23311f57ee
XIP_OFFSET is the hard-coded offset of writable data section within the kernel. By hard-coding this value, the read-only section of the kernel (which is placed before the writable data section) is restricted in size. As a preparation to remove this hard-coded macro XIP_OFFSET entirely, stop using XIP_OFFSET in XIP_FIXUP_FLASH_OFFSET. Instead, use __data_loc and _sdata to do the same thing. While at it, also add a description for XIP_FIXUP_FLASH_OFFSET. Signed-off-by: Nam Cao <namcao@linutronix.de> Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com> Link: https://lore.kernel.org/r/7b3319657edd1822f3457e7e7c07aaa326cc2f87.1717789719.git.namcao@linutronix.de Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
49 lines
1.5 KiB
C
49 lines
1.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* XIP fixup macros, only useful in assembly.
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*/
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#ifndef _ASM_RISCV_XIP_FIXUP_H
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#define _ASM_RISCV_XIP_FIXUP_H
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#include <linux/pgtable.h>
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#ifdef CONFIG_XIP_KERNEL
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.macro XIP_FIXUP_OFFSET reg
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/* Fix-up address in Flash into address in RAM early during boot before
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* MMU is up. Because generated code "thinks" data is in Flash, but it
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* is actually in RAM (actually data is also in Flash, but Flash is
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* read-only, thus we need to use the data residing in RAM).
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*
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* The start of data in Flash is _sdata and the start of data in RAM is
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* CONFIG_PHYS_RAM_BASE. So this fix-up essentially does this:
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* reg += CONFIG_PHYS_RAM_BASE - _start
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*/
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li t0, CONFIG_PHYS_RAM_BASE
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add \reg, \reg, t0
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la t0, _sdata
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sub \reg, \reg, t0
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.endm
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.macro XIP_FIXUP_FLASH_OFFSET reg
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/* In linker script, at the transition from read-only section to
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* writable section, the VMA is increased while LMA remains the same.
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* (See in linker script how _sdata, __data_loc and LOAD_OFFSET is
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* changed)
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*
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* Consequently, early during boot before MMU is up, the generated code
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* reads the "writable" section at wrong addresses, because VMA is used
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* by compiler to generate code, but the data is located in Flash using
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* LMA.
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*/
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la t0, _sdata
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sub \reg, \reg, t0
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la t0, __data_loc
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add \reg, \reg, t0
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.endm
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#else
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.macro XIP_FIXUP_OFFSET reg
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.endm
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.macro XIP_FIXUP_FLASH_OFFSET reg
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.endm
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#endif /* CONFIG_XIP_KERNEL */
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#endif
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